General maintenance is needed by the sounds of it. Try running Disk Utility, & if you have them: Norton Utilities, TechTool Pro & DiskWarrior. Also important to do these things:
SAFE Boot & Repair Permissions.
* Reduce your shares to below 2,000
*
Tip: Purge the Downloads Queue!
* Don't use an external drive for sharing. The QuickSilver doesn't seem to be very good at using it. I have a QuickSilver myself & have had problems with external firewire drives for sharing with LW & other p2p programs.